Vehicle seat

ABSTRACT

In a vehicle seat ( 1 ), a heater element ( 40 ) disposed between the surface of a cushion pad ( 8 ) and a skin member ( 9 ) includes a pair of main body portions ( 45 - 47 ) and a crossing portion ( 48, 49 ) connecting the main body portions to each other, the crossing portion being received in a tuck-in groove ( 11 ) formed in the cushion pad and extending through a gap defined between a bottom portion ( 22 ) of the tuck-in groove and a tuck-in member ( 35 ). The heater element includes a substrate ( 41 ) in sheet form, and a heater wire ( 42 ) attached to the substrate, and the heater wire in the crossing portion extends in a direction orthogonal to a lengthwise direction of the tuck-in groove in a zigzag pattern, the heater wire including a bent portion ( 62 ) of the zigzag pattern located in a bottom region ( 68 ) of the tuck-in groove.

TECHNICAL FIELD

The present invention relates to a vehicle seat fitted with a heaterelement.

BACKGROUND ART

It is known in the field of vehicle seats to interpose a heater elementin sheet form between a cushion pad and a skin member forming a seatcushion or a seat back for the purpose of heating a prescribed part ofthe seat. The heater element typically comprises a substrate in sheetform, and a resistive heater wire printed on the substrate. During theassembly process of the vehicle seat, the heater element is typicallyplaced on the surface of the cushion pad which is formed with a tuck-ingroove, and a part of the heater element crossing the tuck-in groove istucked into the tuck-in groove along with the skin member. SeeJP2014-36730A, for instance.

When the cushion pad is compressed by an occupant seating on the uppersurface of the seat cushion, the cushion pad is compressed, and theupper part of the cushion pad adjoining the tuck-in groove is displaceddownward. As a result, the heater wire in the part of the heater elementcrossing the tuck-in groove is bent. An excessive bending of the heaterwire is not desirable in terms of the durability of the heater wire. Tominimize the bending of the heater element in the tuck-in groove, theheater wire may extend across the tuck-in groove in a wavy pattern or azigzag pattern. However, it has been found that the corners of the wavypattern or the zigzag pattern or portions where the extending directionof the heater wire changes are subjected to concentrated stress so thatthe durability of the heater wire may be impaired after repeatedcompression and decompression of the cushion pad.

SUMMARY OF THE INVENTION

In view of such a problem of the prior art, a primary object of thepresent invention is to provide a vehicle seat fitted with a heaterelement that can improve the durability of the heater element.

To achieve such an object, one aspect of the present invention providesa vehicle seat (1), comprising: a cushion pad (8) provided with atuck-in groove (11); a wire (20) provided in the cushion pad under or ina lower part of the groove; a skin member (9) covering a surface of thecushion pad; a tuck-in member (35) attached to a back side of the skinmember and engaged by the wire, the tuck-in member extending along alength of the tuck-in groove; and a heater element (40) in sheet formprovided between the surface of the cushion pad and the skin member, theheater element including a substrate (41) in sheet form and a heaterwire (42) provided on the substrate, wherein the heater element includesa pair of main body portions (45-47) and a crossing portion (48, 49)connecting the main body portions to each other, the crossing portionbeing received in the tuck-in groove and extending through a gap definedbetween a bottom portion (22) of the tuck-in groove and the tuck-inmember, and wherein the heater wire in the crossing portion extends in adirection orthogonal to a lengthwise direction of the tuck-in groove ina zigzag pattern, the heater wire including a bent portion (62) of thezigzag pattern located in a bottom region (68) of the tuck-in groove.

Thereby, stress concentration on the bent portion of the heater wire canbe minimized. When the cushion pad is compressed under the pressure of aseat occupant, the part of the cushion pad in the bottom region does notdeform so much as the part of the cushion pad adjoining the bottomportion of the tuck-in groove. Therefore, the deformation of the bentportion in the bottom region is relatively small, and stressconcentration in this region can be avoided.

Preferably, the tuck-in member extends linearly along the length of thetuck-in groove, and the bottom region is defined as a region rangingfrom the bottom portion of the tuck-in groove to an upper surface of thetuck-in member.

Alternatively, the tuck-in member extends linearly along the length ofthe tuck-in groove, and the bottom region is defined as a region rangingfrom the bottom portion of the tuck-in groove to a lower surface of thetuck-in member.

Typically, the part of the cushion pad located below the tuck-in memberdeforms considerably less than the upper part of the cushion pad so thatthe bent portion is prevented from being bent to a significant extent,and the durability of the heater wire can be improved.

In preferred embodiment of the present invention, the heater wireincludes a plurality of bent portions in the crossing portion, and allof the bent portions are located in the bottom region.

Thereby, stress concentration in the bent portions can be effectivelyavoided, and the durability of the heater wire can be maximized.

Preferably, the heater wire includes a pair of bent portions located onrespective side wall portions (23) of the tuck-in groove.

By limiting the number of bent portions to two, the durability of theheater wire can be improved without requiring to unduly increase thewidth of the crossing portion. By limiting the width of the crossingportion, the crossing portion can be received in the tuck-in groovewithout causing any irregular deformation of the crossing portion.

Preferably, the heater wire in the crossing portion includes a linearportion (61) extending linearly to form an angle larger than 45° andsmaller than 90° with respect to a direction orthogonal to thelengthwise direction of the tuck-in groove.

As the heater wire extends obliquely in the crossing portion, thebending stress of the heater wire can be minimized.

Preferably, the crossing portion is narrower in width than the main bodyportions, and a corner defined by a side edge of the crossing portionand an opposing edge of one of the main body portion is provided with anextension portion (51-53) of the crossing portion, and the linearportion of the heater wire extends obliquely on the extension portion.

Thereby, the linear portion of the heater wire can be given an adequatelength without unduly increasing the width of the crossing portion as awhole.

Preferably, the bottom portion of the tuck-in groove is provided with aplurality of protrusions (24) arranged along the length of the tuck-ingroove, and the crossing portion is passed through a space createdbetween an adjoining pair of the protrusions.

Thereby, even when the cushion pad adjoining the tuck-in groove iscompressed to a significant extent, the crossing portion is allowed tomove into the gap defined between the two adjoining protrusions so thatthe crossing portion is prevented from deforming in an irregular manner.

Preferably, the crossing portion is narrower in width than the main bodyportions.

Thereby, the crossing portion is allowed to deform in a controlledmanner.

Preferably, a folded portion (65) of the crossing portion is formedadjacent to the bottom portion of the tuck-in groove, the folded portionbeing spaced from the bottom portion.

Thereby, the crossing portion is allowed to deform in a controlledmanner.

BRIEF DESCRIPTION OF THE DRAWING(S)

FIG. 1 is a perspective view of a vehicle seat according to a preferredembodiment of the present invention;

FIG. 2 is a plan view of a seat cushion showing a positionalrelationship between a cushion pad and a heater element;

FIG. 3 is a sectional view taken along line of FIG. 2;

FIG. 4 is a sectional perspective view taken along line Iv-Iv of FIG. 2;and

FIG. 5 is a plan view of the heater element.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

A preferred embodiment of the present invention is described in thefollowing with reference to the appended drawings.

As shown in FIG. 1, the seat 1 includes a seat cushion 5 provided on afloor 2 of a vehicle via a slide rail 3, and a seat back 6 pivotallyconnected to a rear portion of the seat cushion 5. The seat cushion 5 isa main part of the seat 1 for supporting the occupant from below, andthe seat back 6 is a backrest part of the seat 1 for supporting the backof the occupant from the rear.

The seat cushion 5 includes a seat cushion frame (not shown in thedrawings) consisting of a skeletal frame, a cushion pad 8 supported bythe seat cushion frame, and a skin member 9 covering an outer surface ofthe cushion pad 8.

The cushion pad 8 is made of a flexible resin material such as foamedurethane. As shown in FIG. 2, a plurality of tuck-in grooves 11-13 areformed on the upper surface of the cushion pad 8. The tuck-in grooves11-13 each consist of a groove recessed from the surface, and extendingin a predetermined direction. The tuck-in grooves 11-13 include a firsttuck-in groove 11 extending laterally in a middle part of the surface ofthe cushion pad 8 and terminating at some distance from each side edgeof the cushion pad 8, a second tuck-in groove 12 extending laterally inrear end part of the cushion pad 8 and similarly terminating at somedistance from each side edge of the cushion pad 8, and a pair of thirdtuck-in grooves 13 extending in the fore and aft direction and connectedto the respective side ends of the first and the second tuck-in grooves11 and 12.

The lateral ends of the first and the second tuck-in grooves 11 and 12are connected to the third tuck-in grooves 13 in such a manner that thesurface of the cushion pad 8 is separated into a first (front) centralpart 15, a second (middle) central part 16, a third (rear) central part17, and a pair of side parts 18 by the first tuck-in groove 11, thesecond tuck-in groove 12, and the third tuck-in grooves 13. The firstcentral part 15 is defined by the first tuck-in groove 11 and the thirdtuck-in grooves 13, and the second central part 16 is defined by thefirst tuck-in groove 11, the second tuck-in groove 12 and the thirdtuck-in grooves 13. The third central part 17 is defined on the rearside of the second tuck-in groove 12, and the side parts 18 are eachdefined on an outer side of the corresponding third tuck-in groove 13.The first central part 15, the second central part 16, and the thirdcentral part 17 are formed in a substantially planar shape while theside parts 18 each slant upward toward the lateral end thereof.

As shown in FIGS. 3 and 4, a wire 20 consisting of a linear member madeof a metal material or a resin material is provided in the cushion pad 8under or in a lower part of each of the tuck-in grooves 11-13. In eachtuck-in groove 11-13, the wire 20 extends along the lengthwise directionthereof. The wire 20 may be disposed in the cushion pad 8 by insertmolding of the cushion pad 8 using the wire 20 as an insert in theillustrated embodiment.

The first tuck-in groove 11 has a bottom portion 22 and a pair of sidewall portions 23 extending substantially perpendicularly from eitherside of the bottom portion 22. The bottom portion 22 is provided with aplurality of protrusions 24 protruding toward the opening end side andat a regular interval in the longitudinal direction of the first tuck-ingroove 11. In the bottom portion 22, a recess 25 is created between eachadjoining pair of the protrusions 24. Each protrusion 24 is connected tothe side wall portions 23.

The skin member 9 of the seat cushion 5 and the seat back 6 are formedof a sheet material such as woven fabric, leather and synthetic leather.As shown in FIG. 3, the skin member 9 includes a plurality of sheetsections 31 and 32, and is formed by sewing the edges of the sheetsections 31 and 32 with each other. The edges of the respective sheetsections 31 and 32 are sewn together in an overlapping relationship sothat the respective front surfaces thereof are in contact with eachother to form a sewn portion 33. Therefore, the sewn portion 33protrudes to the back surface side with respect to the sheet sections 31and 32. A pull cloth 34 is stitched to the sewn portion 33.

The pull cloth 34 consists of a band-like member extending along thesewn portion 33, and is sewn to the sewn portion 33 at one side edge. Atuck-in member 35 consisting of a linear member extending along the sideedge of the pull cloth 34 is connected to the other side edge of thepull cloth 34. The tuck-in member 35 may also be referred to as asuspender cord. The tuck-in member 35 may extend continuously on theside edge of the pull cloth 34 or may extend intermittently. The tuck-inmember 35 is formed of a material having higher rigidity than the pullcloth 34 such as resin and metal. The tuck-in member 35 is preferablyconnected to the pull cloth 34 by, for example, adhesion or welding.Further, the tuck-in member 35 may be connected to the pull cloth 34 bybeing inserted into a hole formed in the pull cloth 34. In the presentembodiment, the tuck-in member 35 is provided with a substantiallysquare shape, but may also be provided with a circular or other crosssectional shape.

A plurality of engagement members (not shown in the drawings) which mayconsist of hooks, for example, are provided at appropriate portions ofthe edge portion of the skin member 9. The skin member 9 is arranged soas to cover the surface of the cushion pad 8. The edge portion of theskin member 9 extends to the back side of the cushion pad 8, and ishooked onto a structural member provided on the seat cushion frame orthe seat cushion frame itself by means of the engagement members.

As shown in FIG. 3, when the skin member 9 is placed on the cushion pad8, the sewn portions 33 and the tuck-in grooves 11-13 are disposed so asto correspond to each other. The sewn portion 33, the pull cloth 34 andthe tuck-in member 35 are disposed inside the tuck-in grooves 11-13, andthe tuck-in member 35 extends in the lengthwise direction of the tuck-ingrooves 11-13. FIG. 4 is a cross sectional perspective view of the seatcushion, in which the skin member 9 and the pull cloth 34 are omittedfrom illustration. As shown in FIG. 4, the tuck-in member 35 is engagedto the wire 20 by locking members 36. The locking members 36 may eachconsist of a C-shaped clip hooked onto the tuck-in member 35 and thewire 20, or a ring or a tying band integrally surrounding the tuck-inmember 35 and the wire 20. The skin member 9 is thus secured to thesurface of the cushion pad 8 by the tuck-in member 35 being engaged bythe wire 20.

The tuck-in member 35 is positioned with respect to the tuck-in grooves11-13 by abutting against the projecting end of the protrusions 24. Aspace is created between the tuck-in member 35 and the bottom portion 22of the tuck-in grooves 11-13 by the tuck-in member 35 abutting on theprotrusions 24. It can also be said that the space is created by therecesses 25. The tuck-in member 35 is provided with a width which issmaller than the width of the tuck-in grooves 11-13, or the distancebetween the side wall portions 23. As a result, a gap is created betweenthe tuck-in member 35 and each side wall portion 23.

As shown in FIGS. 3 and 4, a sheet-like heater element 40 (seat heater)is provided between the surface of the cushion pad 8 and the skin member9. As shown in FIG. 5, the heater element 40 includes a sheet-likesubstrate 41 and a heater wire 42 attached to the substrate 41.

The substrate 41 is formed of a stretchable sheet member such as anon-woven fabric or a woven fabric. The substrate 41 includes a firstmain body portion 45, second main body portion 46, and a third main bodyportion 47 that are connected in series in a prescribed direction. Thesubstrate 41 further includes a first crossing portion 48 connecting thefirst main body portion 45 to the second main body portion 46, and asecond crossing portion 49 connecting the second main body portion 46 tothe third main body portion 47. In the illustrated embodiment, eachcrossing portion 49 consists of two parallel strips. In the illustratedembodiment, the first main body portion 45, the second main body portion46, the third main body portion 4, the first crossing portion 48, andthe second crossing portion 49 consist of a single piece of continuoussheet material.

The first main body portion 45, the second main body 46, and the thirdmain body portion 47 are each formed in a rectangular shape, and havelong sides extending in a second direction orthogonal to the firstdirection. In the present embodiment, the first main body portion 45 islonger than the second main body portion 46 both in the long sides andshort sides. The second main body portion 46 has a substantially samelength as the third main body portion 47 in the second direction, and islonger than the third main body portion 47 in the first direction.

The first crossing portion 48 and the second crossing portion 49 areformed in a band shape and extend in the first direction. Each crossingportion 48 and 49 may also be considered as a single strip having acentral opening 48 a and 49 a. The first crossing portion 48 is formednarrower than the first main body portion 45 and the second main bodyportion 46, and the second crossing portion 49 is formed narrower thanthe second main body portion 46 and the third main body portion 47. Afirst extension portion 51 is provided at a corner between the firstcrossing portion 48 and the first main body portion 45 on each outerside of the first crossing portion 48 in such a manner that the edges ofthe first crossing portion 48 and the first main body portion 45 arejoined to each other via slanted edges of the respective first extensionportions 51. A second extension portion 52 is provided at a cornerdefined in the central opening 48 a of the first crossing portion 48between the first crossing portion 48 and the second main body portion46 on each outer side of the opening 48 a in such a manner that theedges of the first crossing portion 48 and the second main body portion46 are joined to each other via slanted edges of the respective secondextension portions 52. Similarly as the first extension portions 51, athird extension portion 53 is provided at a corner between the secondmain body portion 46 and the second crossing portion 49 on each outerside of the second crossing portion 49 in such a manner that the edgesof the second main body portion 46 and the second crossing portion 49are joined to each other via slanted edges of the respective thirdextension portions 53. The first to third extension portions 51-53 arethus each provided with a triangular shape.

The heater wire 42 consists of a resistive heater wire that generatesheat when electric current is conducted, and is bonded to the surface ofthe substrate 41 by adhesion or the like. The heater wire 42 extendsfrom a first terminal 56 provided at the rear edge of the third mainbody portion 47 facing away from the second main body portion 46, andthrough the third main body portion 47, the second crossing portion 49,the second main body portion 46, the first crossing portion 48, thefirst main body portion 45, the first crossing portion 48, the secondmain body portion 46, the second crossing portion 49, the third mainbody portion 47 in this order. The heater wire 42 in the third main bodyportion 47 is connected to a second terminal 57 provided at the rearedge of the third body portion 47. Thus, in the present embodiment, twosections of the heater wire 42 extend in the first direction in parallelto each other, and are connected to the first terminal 56 and the secondterminal 57, respectively, at one end, and are connected to each otherat the other end. In the illustrated embodiment, the heater wire 42 infact consists of two heater wires that extend in parallel to each other,but may be treated as a single wire in this disclosure for theconvenience of description. The first terminal 56 and the secondterminal 57 are connected to a wire harness connected to a power sourcealthough not shown in the drawings.

The heater wire 42 extends in the first direction while meandering inthe second direction in the first main body portion 45 and the secondmain body portion 46. In the illustrated embodiment, the heater wire 42is bent in a hairpin shape so as to include sections that extendsubstantially in the second direction in parallel to each other.

In the first crossing portion 48 and the second crossing portion 49, theheater wire 42 extends in the first direction while meandering in thesecond direction. In the present embodiment, the heater wire 42 in thefirst crossing portion 48 is formed in a zigzag shape (waveform) thatincludes a plurality (three) of linear portions 61 extending obliquelywith respect to the first direction, and a plurality (two) of bentportions 62 provided between the adjacent linear portions 61. Eachlinear portion 61 forms an angle larger than 45° and smaller than 90°with respect to the first direction. More preferably, each linearportion 61 forms an angle larger than 45° and smaller than 80° withrespect to the first direction. The absolute values of the angles of therespective linear portions 61 with respect to the first direction may beequal to each other or may be different from each other.

It is preferable that the bent portions 62 of the heater wire 42 in thefirst crossing portion 48 and the second crossing portion 49 are eachformed as an arcuate section. In the present embodiment, there are twobent portions 62 of the heater wire 42 in each of the first crossingportion 48 and the second crossing portion 49. Each of the bent portions62 is disposed at the central part of each individual strip of eachcrossing portion with respect to the first direction. For example, wheneach crossing portion is divided into three equal parts in the firstdirection, the bent portions 62 may be disposed in the central part.

The linear portion 61 of the heater wire 42 in the first crossingportion 48 positioned on the side of the first main body portion 45passes through the first extension portion 51 in extending from thefirst main body portion 45 to the first crossing portion 48. The linearportion 61 of the heater wire 42 in the first crossing portion 48positioned on the side of the second main body portion 46 passes throughthe second extension portion 52 in extending from the first crossingportion 48 to the second main body 46. As a result, the heater wire 42can linearly extend from the first main body portion 45 and the secondmain body 46 without forming any bent portion 62 at either end of thefirst crossing portion 48 in the first direction and without requiringthe width of the first crossing portion 48 to be unduly increased.

The side edge of each first extension portion 51 extends in parallelwith the linear portion 61 passing through the first extension portion51. As a result, the area of the first extension portion 51 required toaccommodate the linear portion 61 can be minimized. Similarly, the sideedge of each second extension portion 52 extends in parallel with thelinear portion 61 passing through the second extension portion 52.

Each linear portion 61 of the heater wire 42 in the second crossingportion 49 located on the side of the second main body portion 46 passesthrough the third extension portion 53 in extending from the second mainbody portion 46 to the second crossing portion 49. As a result, theheater wire 42 can extend linearly from the second main body portion 46without forming any bent portion 62 on the side of the second crossingportion 49 adjoining the second main body portion 46.

As shown in FIG. 2, the first main body portion 45 is arranged on thefirst central part 15, the second main body portion 46 is arranged onthe second central part 16, the third main body portion 47 is arrangedon the third central part 17. The heater element 40 is disposed on thesurface of the cushion pad 8. The first main body portion 45, the secondmain body 46 and the third main body portion 47 may be attached to thefirst central part 15, the second central part 16, and the third centralpart 17, respectively, by using double-sided tape, for example, in eachcase. As shown in FIGS. 3 and 4, the first crossing portion 48 isreceived in the first tuck-in groove 11, and extends across the tuck-ingroove 11 by passing through a gap defined between the bottom portion 22of the first tuck-in groove 11 and the tuck-in member 35. The secondcrossing portion 49 is similarly received in the second tuck-in groove12, and extends across the second tuck-in groove 12 by extending througha gap defined between the bottom portion 22 of the second tuck-in groove12 and the tuck-in member 35.

The first crossing portion 48 passes through the gap defined between thetuck-in member 35 and one of the side wall portions 23 from the open endof the first tuck-in groove 11, and extends toward the bottom portion 22to be received in the recess 25 or, in other words, to pass through thegap defined between the tuck-in member 35 and the bottom portion 22. Thefirst crossing portion 48 forms a folded portion 65 under the tuck-inmember 35 by being bent by 180° in an arcuate shape, and passes throughthe gap defined between the tuck-in member 35 and the other side wallportion 23 before extending to the open end of the first tuck-in groove11. As the first crossing portion 48 is not fixedly secured to eitherside wall portion 23 of the first tuck-in groove 11, the first crossingportion 48 can move along the side wall portions 23 to a certain extent.The two strips of the first crossing portion 48 and the protrusions 24are arranged in an alternating manner along the lengthwise direction ofthe first tuck-in groove 11.

When the heater element 40 is placed on the surface of the cushion pad8, the first direction of the heater element 40 is orthogonal to theextending direction of the first tuck-in groove 11. The heater wire 42of the first crossing portion 48 extends in a zigzag shape in adirection orthogonal to the extending direction of the first tuck-ingroove 11, and extends at an angle to a direction orthogonal to theextending direction of the first tuck-in groove 11, this angle beinglarger than 45° and smaller than 90°.

In the first tuck-in groove 11, a region ranging from the open end tothe surface (edge portion) of the tuck-in member 35 facing the open endis defined as an open end region 67, and a region ranging from thesurface (upper surface) of the tuck-in member 35 facing the open end tothe bottom portion 22 is defined as a bottom region 68. Each of the bentportions 62 of the heater wire 42 in the first crossing portion 48 isdisposed in the bottom region 68, and not in the open end region 67.More preferably, each of the bent portions 62 of the heater wire 42 inthe first crossing portion 48 may be disposed closer to the bottomportion 22 than the surface (lower surface) of the tuck-in member 35facing away from the open end (facing toward the bottom portion 22).

A gap is formed between the folded portion 65 of the first crossingportion 48 and the bottom portion 22. In other words, the folded portion65 faces the bottom portion 22 via a gap. The width of the tuck-inmember 35 is larger than the thickness of the first crossing portion 48,and the distance between the bottom portion 22 and the tuck-in member 35is larger than the width of the tuck-in member 35. Further, a gap isformed between the folded portion 65 of the first crossing portion 48and the tuck-in member 35.

The second crossing portion 49 is arranged in the second tuck-in groove12. The detailed configuration of the second crossing portion 49 in thesecond tuck-in groove 12 is similar to that of the first crossingportion 48 in the first tuck-in groove 11.

The seat back 6 includes a seat back frame (not shown in the drawings)forming a skeletal frame, a cushion pad 71 supported by the seat backframe, a skin member 72 covering an outer surface of the cushion pad 71,and a heater element 73 provided between the cushion pad 71 and the skinmember 72. The configurations of the cushion pad 71, the skin member 72,and the heater element 73 in the seat back 6 are similar to those of thecushion pad 8, the skin member 9, and the heater element 40 in the seatcushion 5.

The features and advantages of the seat 1 configured as described aboveare described in the following. When the seat cushion 5 receives a loaddue to seating of an occupant or the like, the cushion pad 8 iscompressed in the thickness-wise direction. The first tuck-in groove 11is also compressively deformed in the depth direction in accordance withthe deformation of the cushion pad 8. At this time, the deformation ofthe first tuck-in groove 11 is more significant in the open end region67 than in the bottom region 68. This owes to the fact that the bottomregion 68 is located farther away from the front side of the cushion pad8 than the open end region 67, and that the load is supported by thetuck-in member 35 from the outside, so that the load is prevented frombeing transmitted to the side wall portions 23 defining the bottomportion 68. In the seat 1, because the crossing portions 48 and 49 ofthe heater element 40 each pass through the corresponding bottom region68 between the bottom portion 22 and the tuck-in member 35 in thecorresponding tuck-in groove 11, 12, and the load is prevented frombeing applied to the heater element 40, deformation of the crossingportions 48 and 49 is suppressed. As a result, deformation of the heaterwire 42 at the crossing portions 48 and 49 is suppressed, and breakageof the heater wire 42 is prevented.

In each of the crossing portions 48 and 49, the bent portions 62 of theheater wire 42 are positioned in the bottom region 68, instead of theopen end region 67, stress concentration in the bent portions 62 isminimized.

Since the linear portions 61 of the heater wire 42 in the crossingportions 48 and 49 are inclined at an angle larger than 45° and smallerthan 90° with respect to the direction orthogonal to the extendingdirection of the tuck-in grooves 11 and 12, the deformation of thelinear portions 61 of the heater wire 42 owing to the foldingdeformation of the crossing portions 48 and 49 can be minimized.

Since the bent portions 62 of the heater wire 42 are disposed in thebottom region 68, the distance between the adjoining bent portions 62 ofthe heater wire 42 or, in other words, the length of the linear portion61 extending between the adjoining bent portions 62 of the heater wire42 can be minimized. As a result, the bent portions 62 are confined tothe region adjoining the bottom portion 22 so that the bent portions 62are protected from deformation.

Since a gap is formed between the folded portion 65 of each of thecrossing portions 48 and 49 and the bottom portion 22 of thecorresponding tuck-in groove 11, 12, even when the surface portion ofthe cushion pad 8 undergoes a deformation, the crossing portions 48 and49 can slide into the bottom portions 22 of the tuck-in grooves 11 and12 so that the deformation of the crossing portions 48 and 49 can beminimized.

Since the folded portions 65 of the crossing portions 48 and 49 arespaced from the tuck-in members 35, even when the surface portion of thecushion pad 8 is deformed, the crossing portions 48 and 49 and thetuck-in members 35 are prevented from contacting each other so that thedeformation of the crossing portions 48 and 49 can be minimized.

Since each linear portion 61 of the heater wire 42 extending from thefirst main body portion 45 extends to the first crossing portion 48 viathe corresponding first extension portion 51, the linear portion 61extending from the first main body portion 45 can be extended to thebottom region 68 without increasing the width of the first crossingportion 48 (or the individual strip thereof), and the associated bentportion 62 is allowed to be located in the bottom region 68. The same istrue with the second extension portion 52 and the third extensionportion 53.

According to the illustrated embodiment, because each bent portion islocated in the bottom region, instead of the open end region, stressconcentration on the bent portion can be minimized.

Because the heater wire includes a linear portion extending orthogonallyto the lengthwise direction of the tuck-in groove and forming an anglelarger than 45° and smaller than 90° with respect to a directionorthogonal to the lengthwise direction of the tuck-in groove, thedeformation of the heater wire can be minimized even when the cushionpad adjoining the tuck-in groove is highly compressed.

If the heater wire in the crossing portion includes two bent portionsthat are positioned in the bottom region, the bent portions can beplaced close to the bottom portion without requiring to unduly increasethe width of the crossing portion.

By using the tuck-in member that extends linearly along the length ofthe tuck-in groove, the deformation of the cushion pad in the bottomregion can be reduced even further as compared to the open end region.

By providing the protrusions arranged along the length of the tuck-ingroove, the crossing portion is allowed to move into the space definedbetween the protrusions when the cushion pad is compressed under theload of a seat occupant so that the crossing portion is prevented fromdeforming in an irregular manner.

By defining a gap between the folded portion of the crossing portion andthe bottom portion, the crossing portion is allowed to move into the gapwhen the cushion pad is compressed under the load of a seat occupant sothat the crossing portion is prevented from deforming in an irregularmanner.

If the distance between the bottom portion of the tuck-in groove and thetuck-in member is larger than the thickness of the crossing portion, thecontact between the tuck-in member and the crossing portion and/or thecontact between the crossing portion and the bottom portion can beavoided.

By providing a gap between the folded portion of the crossing portionand the tuck-in member, contact between the tuck-in member and thecrossing portion can be avoided when the cushion pad is compressed underthe load of a seat occupant so that the crossing portion is preventedfrom deforming in an irregular manner.

By providing the extension portions between the crossing portion and theadjoining main body portion, the linear portions of the heater wire canbe extended obliquely without requiring the crossing portion to beincreased in width over the entire length thereof.

The side edge of each extension portion may extend in parallel with theheater wire thereon so that the overall area of the extension portionmay be minimized.

Although the present invention has been described in terms of a specificembodiment, the present invention is not limited by the illustratedembodiment, but various parts thereof can be modified and substitutedwithout departing from the spirit of the present invention. For example,the first tuck-in groove 11 traversed by the first crossing portion 48may be configured as a groove extending in the fore and aft directionwith respect to the cushion pad 8.

The invention claimed is:
 1. A method for making a vehicle seat, the vehicle seat comprising a cushion pad provided with a tuck-in groove, a wire provided in the cushion pad under or in a lower part of the groove, a skin member covering a surface of the cushion pad, a tuck-in member attached to a back side of the skin member and engaged by the wire, the tuck-in member extending along a length of the tuck-in groove, a heater element in sheet form provided between the surface of the cushion pad and the skin member, the heater element including a substrate in sheet form having a pair of main body portions and a crossing portion connecting the main body portions to each other, and a heater wire provided on the substrate, the method comprising: arranging the main body portions on the surface of the cushion pad and the crossing portion in the tuck-in groove; arranging the skin member to cover the surface of the cushion pad and the heater element; arranging the tuck-in member inside the tuck-in groove; and engaging the tuck-in member to the wire, wherein the heater wire in the crossing portion extends in a direction transverse to a lengthwise direction of the tuck-in groove in a zigzag pattern, the heater wire including a plurality of bent portions of the zigzag pattern located in a bottom region of the tuck-in groove, and not in an open end region of the tuck-in groove ranging from an open top end of the tuck-in groove opposite the bottom end to an upper surface of the tuck-in member facing the open top end of the tuck-in groove.
 2. A method for making a vehicle seat as defined in claim 1, wherein the bottom end of the tuck-in groove is provided with a plurality of protrusions arranged along the length of the tuck-in groove, the crossing portion is arranged to pass through a space created between an adjacent pair of the protrusions, and the tuck-in member is positioned with respect to the tuck-in grooves by abutting against one or more projecting ends of the protrusions.
 3. A method for making a vehicle seat as defined in claim 1, wherein the tuck-in member is engaged to the wire by one or more locking members.
 4. A vehicle seat, comprising: a cushion pad provided with a tuck-in groove; a wire provided in the cushion pad under or in a lower part of the groove; a skin member covering a surface of the cushion pad; a tuck-in member attached to a back side of the skin member and engaged by the wire, the tuck-in member extending along a length of the tuck-in groove; one or more locking members engaging the tuck-in member to the wire; and a heater element including a substrate in sheet form having a pair of main body portions provided between the surface of the cushion pad and the skin member and a plurality of crossing portions connecting the main body portions to each other, and a heater wire provided on the substrate, wherein the crossing portions being received in the tuck-in groove and extending through a gap defined between a bottom end of the tuck-in groove and the tuck-in member, wherein the heater wire in the crossing portions extends in one or more directions transverse to a lengthwise direction of the tuck-in groove in a zigzag pattern, the heater wire including a plurality of bent portions of the zigzag pattern located in a bottom region of the tuck-in groove, and not in an open end region of the tuck-in groove ranging from an open top end of the tuck-in groove opposite the bottom end to an upper surface of the tuck-in member facing the open top end of the tuck-in groove, wherein crossing portions are positioned away from each other in the longitudinal direction of the tuck-in groove, and wherein one of the locking members engages the tuck-in member to the wire between an adjacent pair of the crossing portions.
 5. The vehicle seat as defined in claim 4, wherein one of the crossing portions is arranged between an adjacent pair of the locking members.
 6. The vehicle seat as defined in claim 4, wherein the bottom end of the tuck-in groove is provided with a plurality of protrusions arranged along the length of the tuck-in groove, the crossing portions are passed through spaces created between adjacent pairs of the protrusions, and the tuck-in member is positioned with respect to the tuck-in grooves by abutting against one or more projecting ends of the protrusions.
 7. The vehicle seat as defined in claim 6, wherein one of the protrusions is arranged between the adjacent pair of the crossing portions.
 8. A method for making a vehicle seat, the vehicle seat comprising a cushion pad provided with a tuck-in groove, a wire provided in the cushion pad under or in a lower part of the groove, a skin member covering a surface of the cushion pad, a tuck-in member attached to a back side of the skin member and engaged by the wire, the tuck-in member extending along a length of the tuck-in groove, a heater element in sheet form provided between the surface of the cushion pad and the skin member, the heater element including a substrate in sheet form having a pair of main body portions and a plurality of crossing portions connecting the main body portions to each other, and a heater wire provided on the substrate, the method comprising: arranging the main body portions on the surface of the cushion pad and the crossing portion in the tuck-in groove; arranging the skin member to cover the surface of the cushion pad and the heater element; arranging the tuck-in member inside the tuck-in groove; and engaging the tuck-in member to the wire by one or more locking members, wherein the heater wire in the crossing portions extends in one or more directions transverse to a lengthwise direction of the tuck-in groove in a zigzag pattern, the heater wire including a plurality of bent portions of the zigzag pattern located in a bottom region of the tuck-in groove, and not in an open end region of the tuck-in groove ranging from an open top end of the tuck-in groove opposite the bottom end to an upper surface of the tuck-in member facing the open top end of the tuck-in groove, wherein crossing portions are positioned away from each other in the longitudinal direction of the tuck-in groove, and wherein one of the locking members engages the tuck-in member to the wire between an adjacent pair of the crossing portions.
 9. The method for making the vehicle seat as defined in claim 8, wherein one of the crossing portions is arranged between an adjacent pair of the locking members.
 10. The method for making the vehicle seat as defined in claim 8, wherein the bottom end of the tuck-in groove is provided with a plurality of protrusions arranged along the length of the tuck-in groove, the crossing portions are passed through spaces created between adjacent pairs of the protrusions, and the tuck-in member is positioned with respect to the tuck-in grooves by abutting against one or more projecting ends of the protrusions.
 11. The vehicle seat as defined in claim 8, wherein one of the protrusions is arranged between the adjacent pair of the crossing portions. 